How to efficiently identify if integer is in wave?

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Hello,

I have wave of integers (16 bit, random order positive integers) and I need to know if a specific integer value is already in that wave.  

First I wrote function which iterates over the wave, but I nearly felt ashamed when I saw the result.

Then I used extract for points which match that integer value and checked the extracted wave length. Still, had to write user function for that.

I still feel there could be some single line solution to this simple issue which is escaping me. Any suggestions? 

Thanks a lot!

 

In the event that your wave contains more than one instance of the integer value (say i_value) you can write in IP9 the following command:

MatrixOP/o/p=1 aa=zapNaNs(replace(equal(myWave,i_value)*IndexRows(myWave),0,nan))

For example:

•make/b/u ddd=trunc(128*sin(2*pi*x/40))
•MatrixOP/o/p=1 aa=zapNaNs(replace(equal(ddd,58)*IndexRows(ddd),0,nan))
  aa={3,17,43,57,83,97,123}  // index points where 58 is found.

In the case of SP/DP data one needs to take into account some tolerance value.  Here is an example:

Redimension/S ddd
ddd+=enoise(0.1)
Variable tol=0.15
Variable value=58
MatrixOP/o/p=1 aa=zapNaNs(replace(greater(tol,abs(ddd-value))*IndexRows(ddd),0,nan))
  aa={3,17,43,57,83,97,123}

 

March 31, 2021 at 10:21 am - Permalink

Great, thanks!

FindValue somehow escaped me, not sure why... And I suspected MatrixOp should be able to help. I need to carefully evaluate that expression. Both solve my problem better than my original solution.  

March 31, 2021 at 12:30 pm - Permalink

Don't forget that in IP8 and later, FindValue has a /UOFV flag which will do the search for the value in multiple threads. If you only care if you have a given value in the wave at least one time, this flag might be appropriate if you're not already running the code in threads.

March 31, 2021 at 01:38 pm - Permalink